Lost airplay icon in control centre!

Hi everybody, this is my first post in your forum so please bare with me if I am off subject. I have multiple apple devices and I am an experienced ( and old) user. Until recently everything was going smoothly. I was able to use airplay to stream YouTube and BBC I player to my Apple TV and everything functioned well. After ios7 things have got a bit strange. I cannot find the icon in individual apps that give me the option to select iPad or Apple TV but worse still I have lost the icon for airplay from control centre? I have checked and updated all devices including iMac - which has also lost the icon to choose Apple TV from iTunes - I sometimes prefer not to stream from the battery challenged devices! I have researched this as much as possible and have been through the restart/ reset till I'm blue in the face. Finally in desperation I went into my local apple store in Montpellier (france) and they swapped it for another one for half price. Considering it was way out of warranty and was just an expensive doorstop I bit and came home with a new one for half price. Imagine my annoyance once connected that it was not even the current software and it spent the next hour updating itself. No change! Everything else works fine - films and YouTube using the Apple TV menu icons and all is well - no streaming from iPad or iPod touch or iMac ( mavericks). Unless you can help me it's another long journey into apple - the genius we saw had never used an Apple TV so I expect not that much of a genius, none of his colleagues had used or seemed to know much about them? This is france so the norm as far as customer service goes, in fact if I'm being honest - way above the norm it's just it doesn't work. Your help would be much appreciated!
Brian

Hi justme'd, thanks for the quick response. All devices including apple TV have the latest version of the operqating system. i did as a precaution read you useful guide to ensure that I had done it correctly. Yes all are fine. still no joy so did another restore but no change.

Just to check a couple things, can you confirm that all of your devices are connecting to the same wireless network? If you have a router that provides multiple access points, make sure that they are connecting to the same one.

How did you set up your Apple TV? Have you tried choosing the "reset" option on the Apple TV to set it up from scratch, then use the iphone method of setting it up? This method is described as soon as you turn on the Apple TV after a factory reset and has worked flawlessly for me every time I've tried it.